Siliplant1 protein precipitates silica in sorghum silica cells. (2nd June 2020)

• Record Type: Journal Article
• Authors: Kumar, Santosh; Adiram-Filiba, Nurit; Blum, Shula; Sanchez-Lopez, Javier Arturo; Tzfadia, Oren; Omid, Ayelet; Volpin, Hanne; Heifetz, Yael; Goobes, Gil; Elbaum, Rivka
• Editors: Vaculik, Marek
• Is Part Of: Journal of experimental botany. Volume 71:Number 21(2020)
• Page Start: 6830
• Page End: 6843
• Publication Date: 2020-06-02
• Subjects: Biomineralization -- phytolith -- silica cell -- silicification -- Siliplant1 (Slp1) -- Sorghum bicolor; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/eraa258
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : This is the first report on a protein, Siliplant1, secreted by plant cells that causes the formation of silica in vivo, owing to its unique primary sequence and charge distribution. Abstract: Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume using an unknown biological factor. Using bioinformatics tools, we identified a previously uncharacterized protein in Sorghum bicolor, which we named Siliplant1 (Slp1). Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. We found Slp1 RNA in sorghum immature leaf and immature inflorescence. In leaves, transcription was highest just before the active silicification zone (ASZ). There, Slp1 was localized specifically to developing silica cells, packed inside vesicles and scattered throughout the cytoplasm or near the cell boundary. These vesicles fused with the membrane, releasing their content in the apoplastic space. A short peptide that is repeated five times in Slp1 precipitated silica in vitro at a biologically relevant silicic acid concentration. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell types. Our results show that Slp1 precipitates silica in sorghum silica cells.